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E. Longhi, N. N. Oiwa, M. Fernandes da Costa, D. Fix Ventura; Psychophysical Evaluation of Retinal Straylight in Healthy Brazilian Subjects. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1551.
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© ARVO (1962-2015); The Authors (2016-present)
To measure retinal straylight in a Brazilian population and to compare it with European norms.
Straylight was assessed using C-Quant that uses an adaptive staircase (Compensation Comparison, Franssen et al., IOVS, 47: 768, 2006). A young (22.2±2.4 yrs, N=20) and an old group (53.8±7.4 yrs, N=21) of subjects were tested. All refractive errors were corrected in the C-Quant apparatus, and no subjects had ocular disease or vision-threatening conditions (e.g., diabetes, unregulated blood pressure, high intraocular pressure, visible cataract). Only 2 subjects in each age group had lightly-pigmented eyes. Each eye was tested 3 times, yielding 6 straylight values (S). Only data fulfilling C-Quant reliability criteria were included.
S values were fit with an empirical equation with 2 free parameters: C, the baseline S-value for young eyes, and V, indicating the age at which S values begin to increase above young-eye values. There were no statistical differences between Brazilian S values and European norms for either young or old age groups (Anova, F= 5.114, p>0.993). However, there was a tendency for our S values to be higher than the European norms: e.g., the young asymptote, C was 9.3 vs 7 for European norms, consistent with young Brazilian eyes having more light-scattering than age-matched European eyes. The age at which Brazilian S values increased (V=70.9 years) tended to occur later than the European norms (V=65).
Consistent with European norms, light-scattering increases with age in the Brazilian sample. This increase is thought to be due, in large part, to age-related changes in lens structure and density. Although the differences between the populations are not significant, the tendency for Brazilian data to have higher S values than European values is in the opposite direction from that expected from a dark-eyed population (darker ==> less scatter). This suggests the hypothesis that latitude-dependent (Sao Paulo, latitude 23ºS, European latitudes between 40ºN to 55ºN) differences in light environment could be associated with differences in S values.
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